The present invention relates to a cutting tool insert for machining by chip removal and wear resistant coating comprising at least one (Zr,Al)N layer with high Zr content grown by physical vapour deposition (PVD) and preferably by cathodic arc evaporation or magnetron sputtering. This insert is particularly useful in metal cutting applications generating high temperatures, e.g., machining of steel, stainless steel and hardened steel.
Zr1-xAlxN (0≦x≦1.0) layers have been synthesized by the cathodic arc evaporation using alloyed and/or metal cathodes, H. Hasegawa et al, Surf. Coat. Tech. 200 (2005). The peaks of Zr1-xAlxN (x=0.37) showed a NaCl structure that changed to a wurtzite structure at x=0.50.
EP 1 785 504 discloses a surface-coated base material and a high hardness coating formed on or over said base material. Said high hardness coating comprises a coating layer containing a nitride compound with Al as main component and at least one element selected from the group consisting of Zr, Hf, Pd, Ir and the rare earth elements.
JP 04-017664 discloses a gradient layer consisting of at least one kind among the carbide, nitride and carbonitride of ZrxAl1-x (0.5≦x≦1.0) in which the Al concentration is continuously or stepwise changed from the interface with the base material toward the surface of the layer.
EP 1 935 999 discloses a cemented carbide end-milling tool with a wear resistant coating. The wear resistant coating comprises a first layer of a PVD AlMe nitride or carbonitride where Me is Zr, V, Nb, Cr or Ti with an atomic fraction of Al to Me between 1.20 and 1.50 and a second layer of PVD AlMe nitride or carbonitride where Me is Zr, V, Nb, Cr or Ti with an atomic fraction of Al to Me between 1.30 and 1.70.
The trends towards dry-work processes for environmental protection, i.e., metal cutting operation without using cutting fluids (lubricants) and accelerated machining speed with improved process put even higher demands on the characteristics of the tool materials due to an increased tool cutting-edge temperature. In particular, coating stability at high temperatures, e.g., oxidation- and wear-resistance, has become even more crucial.
It is an object of the present invention to provide a coated cutting tool insert with improved performance in metal cutting applications at elevated temperatures.
It has been found that a high Zr content in superstoichiometric (Zr,Al)N layers leads to improved high temperature properties and in particular improved crater wear resistance during metal cutting.